The use of microporous materials, including films, in label application for various packaging materials, containers, stationary, blood bags, recording paper, bandages and the like has been described in great detail. The following U.S. Pat. Nos. 6,255,552; 6,162,858; 5,906,830; 5,871,829; 5,583,171; 5,507,525; 5,484,603; 5,314,421; 4,751,087; 4,334,530 and 3,928,099 describe various ways of labeling packaging materials, containers, stationary, blood bags and recording paper wherein sheet materials, e.g., microporous materials, containing additives such as inorganic powder, printing inks, swellable agents, coloring agents, fillers etc. are used to create markings, e.g., etching, scoring, printing, and writing, on the label. In general, these processes require the use of high temperatures and/or the presence of additives within the microporous film in order to display the markings on the surface.
Labeling or printing information on transdermal systems has been a challenge. For example, use of printing inks, coloring agents, solvents and other additives necessary for printing may adversely interact with the active agents within the transdermal system. To address these concerns, transdermal systems have been labeled using a process not requiring the use of inks. The backing layer of the transdermal system is labelled by a thermal embossing process. The polyolefin face of the backing material is melted under pressure to reveal the label.
Notwithstanding some success, the existing technology for labeling transdermal systems has not been entirely satisfactory. The additives in the backing layer and/or the adjacent layers can interact adversely with the active agents. Additionally the use of high temperatures to label the transdermal systems may degrade various components of the transdermal systems or cause adhesive flow beyond the perimeter of the backing. These challenges would in turn affect the potency and stability of the transdermal systems.
Further, the microporous films described previously are directly laminated to a pressure sensitive adhesive to provide labels having good adhesion. However, embossing microporous film after direct lamination to a pressure sensitive adhesive would be problematic. Embossing such microporous films would result in a poorly resolved image due to the slow intrusion of the adhesive into the opaque film layer. The slow adhesive flow into the pores, accompanied by the crushing of the pores due to embossing would render the film transparent. Further, the embossed image would be poorly resolved due to adhesive flow into the pores.